Conventionally, there has been known a light-emitting ceramic that emits light having a wavelength different from that of irradiated light when irradiated with light. Patent Document 1 listed below describes a light-emitting ceramic obtained by heat-treating a ceramic mainly including a pyrochlore type compound represented by ABOW (where A contains at least one selected from the group consisting of La, Y, Gd, Yb, and Lu, B contains at least one selected from the group consisting of Zr, Sn, and Hf and Bi, and W is a positive number for maintaining electrical neutrality) in a reducing atmosphere.
Patent Document 1: WO2014/119416 A1